JPS5941279B2 - microwave oven - Google Patents

Description

[Detailed description of the invention] This invention relates to a microwave oven.

In the conventional microwave oven, as shown in FIG.
In addition, the heating chamber 2 was provided with a turntable 5 and a stirrer fan 6, and the stirrer 7 was formed large at the center of the upper part of the heating chamber.

Figure 2 is a Smith chart, which has a phase scale of the oscillation frequency along its circumferential line, and a standing wave ratio scale along its radial line, which corresponds to the phase of the oscillation frequency. This allows us to know the standing wave ratio. The Smith chart shown in FIG. 2 was observed by the network analyzer N shown in FIG. That is, as shown in FIG. 3, a load A is provided in a desired heating chamber 2, a simulated antenna B having the same structure as the magnetron 3 is fixed to this heating chamber 2, and a sweeper is attached to this simulated antenna B. An oscillation frequency signal is supplied from C through a coaxial cable D, the oscillation frequency is radiated at the simulated antenna B, and the reflected wave reflected at the heating chamber 2 is caught, and the oscillation frequency signal and the reflected wave are combined to produce a stationary signal. A wave is generated on the coaxial cable D, this standing wave is received by the network analyzer body F through the test set E, and it is expressed on the scope G based on this standing wave, and this is observed. . Figure 4 shows magnetron radiote 1
It shows the unnecessary radiation characteristics for the reception frequency band such as noise, and specifically shows the amount of unnecessary radiation divided into regions.

In Figure 4, the unnecessary radiation area is shown on the Smith diagram, and the unnecessary radiation area is divided into 4 areas corresponding to the amount of unnecessary radiation generated.
It is divided into wards, and the tucking density is changed depending on the amount of unnecessary radiation. In FIG. 4, the denser the tucking density, the greater the amount of unnecessary radiation. The Smith chart shown in FIG. 4 shows the characteristics of a particular magnetron, and is provided to the user by the magnetron manufacturer as an attachment to the magnetronograph. By comparing Figure 4 relating to the desired magnetron and Figure 2 relating to the desired impedance of the heating chamber, the user can determine the amount of unnecessary radiation when these magnetrons and heating chambers are combined. I can know. Therefore, by setting the desired impedance of the heating chamber so that its impedance locus is mostly formed in areas where unnecessary radiation is small, the user can reduce unnecessary radiation when the desired heating chamber and magnetron are combined. The amount can be set small.

The above-mentioned unnecessary radiation leaks to the outside of the microwave oven through all the gaps formed between the heating chamber 2 and the outside of the microwave oven, and through the punched holes in the punched plate.

Here, as is clear from comparing FIG. 2 regarding the conventional microwave oven and FIG. The conventional heating chamber 2, when combined with the magnetron shown in Fig. 4, generates a large amount of unnecessary radiation, and this unnecessary radiation leaks from the microwave oven. This was causing noise interference to radios, televisions, etc.

The present invention has been made in view of this point, and will be described below with reference to one embodiment.

In FIG. 5, 8 is an exterior, 9 is a high-frequency heating chamber built into the external device and whose front opening can be opened and closed by a door (not shown), 10 is a magnetron for generating high-frequency radio waves, and 11 is a magnetron. 10 is a waveguide for guiding the generated radio waves to the heating chamber 9; 12 is a blower that takes in air from the component storage chamber 13 and sends the air to the heating chamber 9 after cooling the magnetron 10; 14 is the heating chamber 9; A stirrer fan 15 located at the bottom of the heating chamber is a turntable driven by a motor 16.

In FIG. 6, 17 is a heating chamber intake hole for introducing the wind after cooling the magnetron 10 into the heating chamber 2, and 18 is an intake hole 1.
Starer fan 1 directs the blown air inhaled through 7.
This guide is formed with a stirrer driving air path 19 so as to blow air onto the windshield 4.

The guide 18 is made of a material with low dielectric loss, and its attachment edge 18a is connected to the heating chamber ceiling wall 20.
The heating chamber wall 20 cooperates with the heating chamber wall 20 to form an air passage 19. Reference numeral 21 denotes a vent hole formed in the guide 18, which guides the air after passing through the air path 19 to the center of the heating chamber 2, and discharges it to the outside of the microwave oven along with the steam in the heating chamber 2 through an exhaust hole (not shown). It's functioning.

Reference numeral 22 denotes a high frequency reflection plate, which is arranged at the lower part of the high frequency power supply port 23 and extends from there into the heating chamber 2.

The star fan 14, as shown in FIG.
Starr shaft 24 made of material such as polypropylene
The stirrer shaft boss part 2 is made of material such as Teflon.
5, and attach the wing portion 2 to this starr shaft boss portion 25.
The boss portion 27 of No. 6 is rotatably fitted on the outside, and the boss portion 27 of No.
7 is supported by a washer 28 and a nut 29 to prevent it from falling off.

Furthermore, in this stirrer fan 14, the blade portion 26 is formed so that the dimension X on one side in the radial direction and the dimension Y on the other side in the rotational axis direction are smaller than -(321n0) of the high frequency radio wave wavelength λ.
As shown in FIGS. 8 and 9, a nut 30 is attached to the heating chamber ceiling wall 20 at a location one distance away from the power supply port surface 23'.
I'm so enlightened.

In addition, at least a portion 26a of the wing portion 26 is set to protrude from the front surface of the power feeding port 23 so as to be directly exposed to high-frequency radio waves. FIG. 10 shows the change in load impedance when the turntable 15 and stirrer fan 14 are driven to perform high-frequency heating in the above embodiment.

In this example, regarding the impedance locus 31, it has been confirmed that the impedance locus 31 moves along an arc-shaped movement path 31a while rotating slightly on its axis, as shown in FIG. It has also been confirmed that the arc-shaped movement path 31a varies depending on the mode of the turntable 15, and that the rotation trajectory varies depending on the mode of the stirrer fan 14. Here, since the turntable 15 is circular, there is no apparent movement even when it rotates, which seems to be unrelated to the impedance characteristics, but in reality, radio waves that have entered the bearing part (not shown) of the turntable 15 are transmitted to this bearing part. Because it is stirred at low speed,
Regarding impedance characteristics, there is a relationship as shown in FIG. 10 above.

The design procedure performed in connection with the prevention of unnecessary radiation in this embodiment will be explained below.

In this embodiment, a magnetron 10 having the characteristics shown in FIG. 4 is selected, and the impedance of the heating chamber 9 is set in accordance with the characteristics of the magnetron 10.

First, the impedance movement path 31a related to the rotation of the turntable 15 is set in a region where unnecessary radiation is small as shown in FIG.

Specifically, the moving path 31a is set by adjusting the mode of the turntable 15 or by providing a suitable reflector in the heating chamber 9. Next, the rotation locus 31 according to the aspect of the starrer fan 14 is set. Stara fan 1 here
Regarding the dimensions X and Y of the wing portion 26 of No. 4, the rotation locus of impedance when the dimensions X and Y are changed has been confirmed as follows.

That is, when the dimensions X and λY of one side and/or the other side of the wing section 26 are made the same, the rotation locus mode becomes exactly as shown in FIG. It has been confirmed that if X and λY are reduced, and conversely, X and λY are gradually increased from 1, the rotational diameter a gradually expands, and the shape of the force-rolling trajectory becomes greatly disturbed, similar to the trajectory shape of the conventional example.

Therefore, in this embodiment, we first consider setting the above-mentioned X and Y dimensions to 1 or less so as not to disturb the shape of the rotation λ locus 31.

Regarding the aspect of the above-mentioned rotation locus, if the dimensions X and Y of the wing portion 26λ are gradually increased from 1, the rotation locus will expand and protrude from the region where unnecessary radiation is small, and its shape will become complicated, and the size will further increase. Is it confirmed that when the λ laws X and Y are made equal, the rotation trajectory has no regularity at all? It is.

Further, it is preferable that the dimensions X and Y of the wing section 26 are set to -λ, but if they are set to -λ, electric discharge will occur between the wing section 26 and the heating chamber wall 20, and the dimension X of the wing section 26 As for the lower limit of , Y, we conducted an experiment taking into consideration the radio wave stirring effect, etc., and found that
It has been confirmed that up to 20 steps is preferable. Therefore, in this embodiment, λ is less than 1 by further limiting the above X and Y dimensions.
Set to an appropriate value within the range of 20 mm.

After determining the stirrer dimensions X and Y as described above, the mounting position of the stirrer fan 14 is set.

An experiment regarding the mounting position of the stirrer fan 14 revealed that when a part 26a of the wing section 26 is extended to the front surface of the power feeding port 23 and the distance λz between the power feeding port surface 23' and the wing section 26 is the same, It was confirmed that the rotational diameter A becomes the maximum, and therefore the radio wave stirring effect becomes the maximum.

The amount of change in the rotational diameter a due to the installation position of the starrer fan 14 is extremely small λ, so even when the distance z is set to be the same, the rotation trajectory mode does not change much in terms of size compared to that shown in Fig. 4. It has been confirmed that there is no

Therefore, in this example. Wing section 26 of star fan 14
is formed to be smaller than 1 in terms of dimensions λ of one side in the radial direction and the other side in the rotational direction, and the stirrer fan 1 is
4 is placed at a location approximately λ apart from the feed port surface 23'.

Since the present invention is configured as described above, it is possible to suppress unnecessary radiation and prevent the generation of noise radio waves, and it is also possible to reduce the stirrer fan and thereby increase the storage capacity of the heated object in the heating chamber.

[Brief explanation of the drawing]

Figure 1 is a schematic front view of the conventional example, Figure 2 is a direct view of the load impedance characteristics of the secondary example as seen using a network analyzer, Figure 3 is an explanatory diagram of the method for measuring the impedance of the heating chamber, Figure 4 shows the unnecessary radiation area.
FIG. 5 is a schematic front view of an embodiment of the present invention, FIG. 6 is a transparent perspective view of a part of the embodiment, FIG. 7 is a front view of essential parts of the embodiment, and FIG. 8 9 is a schematic side view of the same embodiment, and FIG. 10 is a direct view of the load impedance characteristics of the same embodiment. 9... High frequency heating chamber, 14... Starer fan, 1
5... Turntable, 23'... Power supply port surface, 26
...Blade portion, X...Dimension of one side in the radial direction, Y...Dimension of the other side in the direction of the rotation axis.

Claims (1)

[Claims] 1. In a high-frequency heating chamber equipped with a stirrer fan and a turntable, the blade portion of the stirrer fan is set to (1/4) of the high-frequency radio wave wavelength with respect to the dimensions of one side in the radial direction and the other side in the direction of the rotational axis. In addition to making the stirrer fan smaller in size, the stirrer fan can be made to
4) A microwave oven characterized in that the microwave oven is placed at a location separated by 4).